These sizes are basically gag sizes to draw for fun based on a sequence or joke (or when drawing the waitress for "Juggalos" . I don't like to draw them that often usually because there's not much posing that can be done with these. Also, since the focus tends to be on the boobs, the face doesn't get as much attention, which is something of an issue with me since my opinion on a picture usually begins with the face (not to mention a pretty face makes boobs all the more enjoyable).

For those who don't get the meaning behind the "Juggalos" reference, please take a look at this:

Oh, but it's very much the same because both situations rely on the support of your spine. The arms are connected at the shoulders to the upper torso, which come to think of it, is a much more intricate connection as opposed to breasts hanging off the pectorals. If I'm holding something large with both arms close to my chest and whatever I'm holding gets heavier than what I can carry, it's gonna bring down my arms, which is gonna bring down my upper torso.

I've never seen someone with breasts the size of beanbags, but I'm fairly certain that heavy lifting would be an impossibility all the same going by your first statement. Heck, my spine would've snapped in half long ago by that logic.

It's usually around giga that i start thinking along the lines of "not sure if gusta" buuut sometimes my brain has other plans… sometimes to the point that i get slightly worried about my mental health (depending on how long it was since my last... You know, this can get to Tengen Toppa Gurren Lagann sizes)